This invention relates to a multi-layer film which has excellent properties such as hygienic nature, flexibility, transparency, heat resistance, bag drop strength, heat seal aptitude and pin hole resistance and to a medical bag which comprises the multi-layer film and is used as a container such as of drug solutions and blood samples.
Currently, hard containers made, for example, of glass, polyethylene or polypropylene and soft bags made of polyvinyl chloride containing a plasticizer are known as medical containers. However, in the case of the former hard containers, it is necessary to introduce air using an infusion set equipped with an air needle or air vent when the included liquid is dripped. In addition, there is a possibility of causing pollution of the included liquid. Also, hard containers made of polyethylene or polypropylene have a problem in that it is difficult to see amount of the included liquid because of their insufficient transparency.
On the other hand, the latter soft bags have advantages in that they do not require the introduction of air such as the case of the hard containers and they have high safety and carrying convenience due, for example, to deflation of the bag itself by the atmospheric pressure with dripping of the included liquid. However, they have a problem in that the plasticizer and residual monomers contained in the polyvinyl chloride are precipitated as fine particles in the included liquid. Thus, a substitute for such a material is expected.
Contrary to this, a medical bag in which an ethylene-vinyl acetate copolymer, an elastomer or the like polymer is used in the intermediate layer has been proposed from flexibility, transparency, hygienic nature and the like points of view (JP-A-58-165866; the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) but, being poor in heat resistance, such a polymer to be used in the intermediate layer has a disadvantage in terms of poor appearances such as formation of wrinkles at the time of sterilization or reduction of transparency after sterilization. In addition, it sometimes causes other problems such as generation of pin holes at the time of transportation and breakage of the bags when they are dropped.
On the other hand, JP-A-6-171039 proposes a multi-layer film in which a polypropylene resin is used in the outer layer and a conventional straight chain ethylene-xcex1-olefin copolymer is used in the intermediate layer, and JP-A-9-141793 proposes a multi-layer film in which a polypropylene resin is used in the outer layer and an ethylene-xcex1-olefin copolymer having a single melting point produced using a metallocene catalyst is used in the intermediate layer. However, transparency, strength, flexibility and heat resistance of the medical bags comprising these multi-layer films are not well-balanced at high levels.
In addition, since a material having heat resistance is arranged in the inner layer from the viewpoint of heat resistance, there is almost no difference in melting point between the outer layer and inner layer, thus causing a problem in that the working efficiency is reduced due to taking of the outer layer by a seal bar at the time of bag making (adsorption of the outer layer to the upper side seal bar).
Thus, medical bags free from the problems, namely those which have good hygienic nature, excellent flexibility and transparency, high heat resistance, good strength against bag breakage when dropped and excellent heat seal aptitude, have not been achieved by the conventional multi-layer medical bags.
In view of the above, it therefore becomes an object of the invention to provide a multi-layer film which has high hygienic nature and excellent flexibility, transparency and pin hole resistance, and also has excellent heat seal aptitude and good heat resistance and bag drop strength, and a medical bag which comprises the multi-layer film and is used as a container such as of drug solutions and blood samples.
As a result of intensive studies, the present inventors have accomplished this invention by finding that the just described object of the invention can beachieved by a multi-layer film which contains at least a first layer and a second layer inside thereof, in which a polyolefin resin composition is used in the first layer, and an ethylene-xcex1-olefin copolymer which comprises a lower crystalline component and a higher crystalline component and has a specified melt flow rate (to be referred to as xe2x80x9cMFRxe2x80x9d hereinafter) and specified properties is used in the inside second layer.
That is, the object of the invention is achieved by a multi-layer film which comprises at least a first layer and a second layer inside thereof, wherein
the first layer comprises a polyolefin resin composition, and
the second layer comprises a polyethylene resin material comprising a copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms, the copolymer comprising a lower crystalline component and a higher crystalline component and satisfying the following physical properties (B1) to (B4):
(B1) in a temperature rising elution fraction (TREF) elution curve of the copolymer, an elution peak temperature of the lower crystalline component is from 45 to 85xc2x0 C.,
(B2) in the temperature rising elution fraction (TREF) elution curve of the copolymer, an H/M value is 9 or more, wherein H is a peak height of the lower crystalline component and M is a height of the minimum valley between the lower crystalline component peak and higher crystalline component peak,
(B3) area ratio of the elution peak temperature or less of the lower crystalline component is 35% or more based on the total area of the temperature rising elution fraction (TREF) elution curve of the copolymer, and
(B4) a melt flow rate (MFR) of the copolymer is from 0.1 to 20 g/10 minutes.
More preferred are the following first and second embodiments.
That is, a first embodiment of the invention provides a multi-layer film which contains at least an outer layer, an intermediate layer and, more preferably, an inner layer in that order, wherein the outer layer comprises a polyolefin resin composition, and the intermediate layer comprises a polyethylene resin material including a copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms, the copolymer containing a lower crystalline component and a higher crystalline component and satisfying all of the following physical properties (B1) to (B4)
(B1) in an elution curve obtained by temperature rising elution fraction of the copolymer, an elution peak temperature of the lower crystalline component is from 45 to 85xc2x0 C.,
(B2) in the elution curve obtained by temperature rising elution fraction of the copolymer, an H/M value is 9 or more, wherein H is a peak height of the lower crystalline component and M is a height of the minimum valley between the lower crystalline component peak and higher crystalline component peak,
(B3) an area ratio of the elution peak temperature or less of the lower crystalline component is 35% or more based on the total area of the elution curve obtained by temperature rising elution fraction of the copolymer, and
(B4) a melt flow rate of the copolymer is from 0.1 to 20 g/10 minutes.
The invention also provides the multi-layer film, wherein the inner layer comprises a resin material selected from the group consisting of a polypropylene resin; a high-pressure low density polyethylene having an extrapolation melting completion temperature of melting peak, obtained by a differential scanning calorimetry (DSC), of 110xc2x0 C. or more; and a copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms, having a density of 0.920 g/cm or more.
The invention also provides the multi-layer film, wherein the lower crystalline component of the copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms in the intermediate layer is polymerized using a metallocene compound containing a tetravalent transition metal, as a polymerization catalyst.
The invention also provides a medical bag which comprises any one of the above multi-layer films of the first embodiment.
A second embodiment of the invention is a multi-layer film which comprises at least an outer layer and an inner layer in that order, wherein the outer layer comprises a polyolefin resin material preferably satisfying the following physical property (A1), and the inner layer comprising a polyethylene resin material including a copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms, the copolymer comprising a lower crystalline component and a higher crystalline component and satisfying all of the following physical properties (B1) to (B4) and, preferably, (B5)
(A1) Vicat softening temperature Ta is Tb less than Taxe2x89xa6140xc2x0 C.,
(B1) in a temperature rising elution fraction (TREF) elution curve of the copolymer components, an elution peak temperature of the lower crystalline component is from 45 to 85xc2x0 C.,
(B2) in the temperature rising elution fraction (TREF) elution curve of the copolymers, an H/M value is 9 or more, wherein H is a peak height of the lower crystalline component and M is a height of the minimum valley between the lower crystalline component peak and higher crystalline component peak,
(B3) an area ratio of the elution peak temperature or less of the lower crystalline component is 35% or more based on the total area of the temperature rising elution fraction (TREF) elution curve of the copolymer component,
(B4) MFR of the copolymer component is from 0.1 to 20 g/10 minutes, and
(B5) Vicat softening temperature Tb is from 65 to 125xc2x0 C.
Also, the invention is the multi-layer film, wherein the outer layer comprises a resin material selected from the group consisting of a polypropylene resin which satisfies the above physical property; a high-pressure low density polyethylene having an extrapolation melting completion temperature of melting peak, obtained by a differential scanning calorimetry (DSC), of 110xc2x0 C. or more; and a copolymer of ethylene with an xcex1-olefin having from 3 to 18 carbon atoms, having a density of 0.910 g/cm3 or more.
Also, the invention also provides a medical bag which comprises any one of the above multi-layer films of the second embodiment.